1. Field of the Invention
The invention relates to a device for rotating a rotary frame supporting at least one reversing roll for a running web.
2. The Prior Art
A device for guiding running webs of material is known from German Patent Application 31 25 852 C1. This device is formed by a rotary frame, on which two rolls are rotatably supported. For this purpose, the rotary frame has two curved guide tracks that cooperate with rollers and are supported in a stationary frame. The curved guide tracks have a common center point of the curvature forming an axis of rotation of the rotary frame. The axis of rotation of the rotary frame is displaceable within wide limits by aligning the guide tracks accordingly. It is also possible with this known device to shift the axis of rotation of the rotary frame to the point where the web of material is running up on the first roll. This results in an advantageous way of influencing the run of the web. This known device is successfully employed in practice. However, a disadvantage is that the guide tracks have to be aligned with each other precisely to obtain rotational motion free of jamming. This is difficult to accomplish especially in conjunction with large rotary frames.
An object of the present invention is to provide a device that permits swiveling of the rotary frame without obstructing the run of the web, and can be manufactured in a simple manner and at favorable cost.
This and other objects are accomplished by providing a device having a rotary frame supporting at least one reversing roll for a running web. Depending on the position of the axis of rotation of the rotary frame in relation to the running web of material, the reversing roll leads to a sideways shifting of the tension of the web. To obtain control over the run of the web, or over its tension, the axis of rotation of the rotary bearing is located as close as possible to the point where the material web runs up on the reversing roll. To prevent the travel of the web from being obstructed by the pivot bearing of the rotary frame, the bearing is designed in the form of an antifriction bearing that is cut in the form of a segment. The position of the cut through the antifriction bearing is selected in such a way that the material web is closely guided across the surface of the area of the cut extending through the antifriction bearing. Furthermore, the antifriction bearing offers the advantage of a bearing having particularly low friction because the only friction being generated is the rolling friction occurring between the rolling elements of the antifriction bearing and the raceways of the bearing boxes, rotating against each other. It is possible to use any known antifriction bearing, such as ball bearings, cylinder bearings, needle bearings, cone bearings and drum-type bearings. Preferably employed is a standard antifriction bearing that is manufactured in large quantity and thus at favorable cost. The bearing is cut to a segment-like shape so that it does not interfere with the run of the web.
If the device is used for shifting the material web sideways, the material web generally runs up on the reversing roll in the direction of the axis of rotation of the rotary frame. It is advantageous if the antifriction bearing of the rotary frame is cut having an approximately axial section. Therefore, the surface of the cut through the antifriction bearing is aligned approximately parallel to the moving material web so that the greatest area of the antifriction bearing is available for supporting radial bearing forces in accordance with the installation conditions.
It is advantageous to place the axis of rotation of the rotary frame as precisely as possible in the material web running up on the reversing roll. The pivot bearing is cut in such a way that its bearing boxes extend over an angle of less than 180xc2x0 so that it will not obstruct the run of the web. The axis of rotation is accordingly located outside the antifriction bearing so that the material web passing through the axis of rotation is guided with a spacing from the antifriction bearing. Furthermore, this results in the additional advantage that two cut antifriction bearings can be obtained from one conventional antifriction bearing, whereby each of the bearings comprises an angle of less than 180xc2x0.
The antifriction bearing normally has rolling elements in the form of balls, needles or rollers, which are kept spaced apart from one another in a cage. When the bearing boxes of the antifriction bearing are swiveled, the cage has a relative movement in relation to the bearing boxes. To prevent the cage from obstructing the run of the web as this relative movement is taking place, the cage extends over a smaller angle than the bearing boxes. The extent to which the cage has to be cut depends on the position of the material web and the required range of the angle of swivel of the rotary frame. Therefore, the cage is cut shorter when the material web travels closer to the antifriction bearing, and the greater the range of the angle of swivel of the rotary frame. In connection with angles of swivel that are greater than 5xc2x0, it is advantageous if the bearing box is cut to a secant- or segment-shaped form.
In cases in which the antifriction bearing comprises an angle of less than 180xc2x0, the bearing boxes of the antifriction bearing can no longer be kept against each other without implementing additional measures. If the bearing boxes of the antifriction bearing are radially pressed against each other by either the tensile force of the material web, or by the force of the weight of the rotary frame and the reversing roll, it makes no difference because the bearing boxes are kept against each other by a radially acting force. In other installation positions, it is necessary to hold the bearing boxes of the antifriction bearing against each other with at least one holding means in the form of a sliding component, or with the help of a rotatable roller. This holding means is connected with one of the bearing boxes in a fixed manner and applies pressure to the other bearing box on the side located opposite the rolling elements of the bearing. With installation positions in which the holding means is required to exert only a low force of pressure, the holding means can be realized in the form of a sliding component because the latter will generate only minor forces of friction. However, with higher forces of pressure, designing the holding means in the form of a rotating roller supported on balls is preferable for reducing the frictional forces generated in the present case.
So as to be able to precisely align the holding means vis-à-vis the antifriction bearing, it is favorable if such a holding means is mounted in an adjustable manner on a cam. In this way, the holding means can be aligned versus the antifriction bearing in a very precise way by simply turning the cam. In particular, the sliding component or the roller can be re-adjusted if this should be required due to wear appearing in the course of operation.
In conjunction with large rotary frames, it is not useful when the entire force of its weight is supported in one single pivot bearing because the pivot bearing and the rotary frame would have to be in a very solid form, which in turn would have a negative effect on the masses to be moved. Therefore, to quickly swivel a large rotary frame, it is advantageous if the frame is supported on a support plate by at least one sliding component or at least one roller so that the rotary frame can be designed with a relatively light weight. The sliding component or the roller are spaced from the swivel axis so that good support of the rotary frame is obtained. Preferably, two sliding components or two rollers are provided which in conjunction with the pivot bearing, will result in a highly stable three-point support of the rotary frame. The sliding components or the rollers support forces directed axially in relation to the axis of rotation so that curved guides on the support plate are not needed. This dispenses with the necessity of having to align the support plate precisely on the pivot axis. Therefore, assembly is very simple in spite of the fact that sliding components or rollers are needed.
Finally, it is preferred if the sliding component or the roller is opposed by another sliding component or by another rotating roller for supporting the rotary frame. This additional sliding component or roller is supported on the opposite side of the support plate. In this way, the sliding components or rollers are capable of absorbing axial tensile forces in addition to axial forces of pressure so that the device can be installed and operated overhead as well without causing any problems.